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Genetic interactions between KAR2 and SEC63, encoding eukaryotic homologues of DnaK and DnaJ in the endoplasmic

M A Scidmore1, H H Okamura, M D Rose

  • 1Department of Molecular Biology, Princeton University, New Jersey 08544-1014.

Molecular Biology of the Cell
|November 1, 1993
PubMed

Insights

Yeast KAR2 and SEC63 proteins, essential for endoplasmic reticulum protein translocation, genetically interact. These interactions suggest Kar2p and Sec63p function together, similar to bacterial DnaK and DnaJ chaperones.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • KAR2 encodes yeast Kar2p, the endoplasmic reticulum (ER) resident HSP70 homolog.
  • Sec63p is an ER integral membrane protein homologous to E. coli DnaJ.
  • Both Kar2p and Sec63p are crucial for protein translocation across the ER membrane.

Purpose of the Study:

  • To investigate the functional relationship between Kar2p and Sec63p.
  • To elucidate the mechanism of protein translocation in yeast.

Main Methods:

  • Analysis of genetic interactions between KAR2 and SEC63 mutations.
  • Characterization of temperature-sensitive mutations and dominant suppressors.
  • Measurement of KAR2 mRNA levels in response to sec63-1 mutation.

Main Results:

  • Temperature-sensitive mutations in KAR2 and SEC63 exhibit synthetic lethality.
  • Dominant KAR2 mutations suppress the temperature-sensitive growth and translocation defects of sec63-1.
  • The sec63-1 mutation induces KAR2 mRNA levels, unlike other translocation mutants.

Conclusions:

  • Kar2p and Sec63p interact genetically in vivo.
  • This interaction is analogous to the bacterial DnaK/DnaJ chaperone system.
  • The Kar2p-Sec63p interaction is critical for their function in protein translocation.

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